1. Field of the Invention
The present invention relates to improvements in a vehicular heat-pump type air conditioner provided with a vapor compression refrigeration cycle, and more particularly to a heat pump type air conditioner having a compressor of a variable discharge capacity type.
2. Description of the Related Art
A variety of vehicular heat-pump type air conditioners have been proposed, for example, in Japanese Patent Provisional Publications Nos. 1-296056 and 2-290475. Each of conventional air conditioners is provided with a vapor compression refrigeration cycle and is arranged to execute a heating operation by utilizing engine waste heat. Furthermore, in order to improve the heating characteristic without utilizing such engine waste heat, inventors of the present invention have proposed a new type air conditioner of a heat-pump type. The new type air conditioner is provided with a heat-radiating inner heat exchanger in addition to a heat-absorbing inner heat exchanger and is arranged to change an operation mode by controlling a three-way valve.
These air conditioners are arranged to change the refrigerant discharge amount of a compressor by changing a rotation speed or discharging capacity of the compressor according to the condition of the refrigeration cycle. The change of the refrigerant discharge amount is executed by a passenger's operations such as starting and stopping of the compressor and switching of cooling operation and heating operation, and by an automatic changing operation of the system according to the condition of the refrigerant cycle.
However, in such air conditioners, the refrigerant discharge amount is changed by single changing rate (or changing speed). Accordingly, if the compressor is of a type which slowly changes the refrigerant discharge amount for protecting the compressor or keeping the stable operation of the refrigeration cycle, it is not easy for the passenger to recognize as to whether the refrigerant discharge amount is actually changed according to a command to the compressor such as start and stop commands and the switching of operation mode, or not.